The radio frequency transmission technology is applied to a radio frequency front-end system of a mobile terminal. The structure of the radio frequency front-end system of the mobile terminal will be described as follows.
As the 3G technology has basically matured at present, domestic operators are mainly popularizing 3G mobile terminal products with a variety of standards. Mobile communication systems with the Time Division Synchronous Code Division Multiple Access (TD-SCDMA) standard are operated by the largest domestic mobile operator, China Mobile. At present, China Mobile is making efforts to popularize the next generation mobile standard of TD-SCDMA, TDD-LTE. Therefore, it can be predicted that coexistence of three standards, GSM, TD-SCDMA and LTE, in the same mobile terminal is required in mobile terminal products for a future long period of time, that is, the design for radio frequency front-end systems of mobile terminals in the future is required to meet the requirement of the coexistence of multiple mode standards.
In a common mobile terminal such as a mobile phone, there is typically a power amplifier (PA), which is a core part in a hardware circuit of a radio frequency front-end system. The PA is responsible for amplifying a final radio frequency modulated signal to a large enough power to facilitate antenna emission at the back-end. The basic radio frequency link structure of the entire radio frequency front-end system of a mobile phone is as shown in FIG. 1. The mobile phone in FIG. 1 supports the GSM or TDD standard.
All PA products in the market are of single standards presently. If the mobile phone is required to support multiple mode standards, a plurality of PAs which support different types of standards respectively must be used. A block diagram of an example of a radio frequency front-end system of a TD and GSM dual-mode mobile phone is shown in FIG. 2.
In summary, if a mobile terminal meeting the requirement of the coexistence of multiple mode standards, such as a mobile terminal compatible with GSM, TD and LTE, is required to be designed in the future, according to the existing design idea of the single standard described above, at least three discrete PA modules will be used for the multiple standards, so as to support their respective standards. This will undoubtedly increase design difficulty and production cost of the entire RF front-end system. Therefore, in order to avoid increase in design complexity and production cost of the entire radio frequency front-end system due to the design complexity of the PA, an equipment manufacturer which designs such a radio frequency front-end system further needs to make the integration design requirement to be the future design trend on the basis of the compatibility of the coexisting multiple mode standards, that is, both the compatibility requirement of the coexisting multiple mode standards and the integration design requirement can be satisfied.
A radio frequency transmission device in an existing radio frequency front-end system of a mobile terminal is used as a core device of the radio frequency front-end system, a PA module inside which will be described as follows.
The existing GSM PA generally uses Multi-chip Module (MCM) packaging. The PA module is composed of a printed circuit board (PCB), a main amplifier chip, a control chip and a plurality of passive matching elements, as shown in FIG. 3.
Since the GSM standard is divided into two frequency bands, in the prior art, main amplifier chips can be manufactured altogether, but output matching circuits are still fabricated in branches of different frequency bands. In addition, SMDs (surface mounted devices) are required in the matching elements. If various frequency bands, such as TD and LTE, are required to be integrated into the PA module in the future, then one output matching circuit is required to be fabricated for each frequency band according to the above existing design idea that output matching circuits are fabricated in branches of different frequency bands, thus multi-branch input/output matching circuits will result in increase in the design complexity of the PA module. The internal structure of the existing multi-mode PA is as shown in FIG. 4. Moreover, the increase in the design complexity of the PA module will inevitably result in increase in the complexity of routing of internal circuits of the radio frequency transmission device, and accordingly the complexity of external pins of the radio frequency transmission device will increase.
In summary, because using the prior art, neither the compatibility requirement of the coexisting multiple mode standards nor the integration design requirement can be satisfied well, the system design complexity and production cost can not be decreased fundamentally. Therefore, there is an urgent need for a new radio frequency transmission device to better meet this requirement, so as to decrease the system design complexity and production cost radically.